Asynchronous Digital Subscriber Line (“ADSL”) is a technology that overcomes some of the limitations of plain old telephone service (“POTS”). A central office can connect to a customer premises via a transmission line, such as a traditional twisted-pair copper line. Once at the customer premises, the transmission line may connect to wiring within the customer premises. The customer wiring may split into more than one branch, and the branches may run to various different locations within the customer premises. ADSL devices, such as phones, computers, and other devices can connect to the customer wiring branches. Through the customer wiring, the ADSL devices can interface with the central office and engage in an ADSL session. In order to communicate with the central office using ADSL, an ADSL device establishes an ADSL session with the central office.
As part of negotiating the ADSL session, the ADSL device and the central office lock to a timing reference, such as a pilot signal generated by the central office or the ADSL device. The ADSL device and the central office communicate with each other by sending data. Bits of data are generally sent as symbols, which can be further grouped into frames. The ADSL device and the central office use the pilot signal in order to accurately determine the alignment of the symbols, thereby each other to accurately send and receive data.
In addition to the ADSL device, other devices may also be located on the customer premises. While the ADSL device and the central office engage in an ADSL session, the other devices may want to use ADSL to exchange data. For example, two other devices on the customer premises may want to use ADSL to exchange data with each other while the ADSL device and the central office continue to engage in their ADSL session.
As the other devices share common data links with the ADSL device, such as wiring within the customer premises, their communication may interfere with the session between the ADSL device and the central office. This is particularly true when the other devices are not aligned with the symbols and frames in the ADSL session, and as these other devices did not engage in the negotiation procedure for the ADSL session, they would generally not be aligned with the symbols and frames for the ADSL session. Thus, their exchange of data would not be aligned with the symbol and frames in the ADSL session, and this can cause interference with the ADSL session.
Therefore, there exists a need for an improved method for aligning symbols in a preexisting ADSL data exchange.